Control method of alternating current-direct current converter and power equipment

Abstract

The invention relates to a control method of an AC / DC converter, and the method comprises the steps: controlling a balance bridge circuit to continuously work in each AC period for energy transmission under the condition that the AC side current is detected to be half-wave current, for example, a half-wave load is provided; the situation that the energy transmission process of the balance bridge circuit is concentrated in a half alternating current period, consequently, midpoint balance current overcurrent is caused, wave-by-wave current limiting is triggered, and then the maximum half-wave load carrying capacity of a system is affected is avoided. Therefore, according to the control method of the AC / DC converter provided by the embodiment of the invention, the half-wave load carrying capacity of the AC / DC converter is improved.

Description

Technical Field

[0001] The present application belongs to the field of power electronics technology, and in particular, relates to a control method of an AC / DC converter, a power device, and a computer-readable storage medium. Background Art

[0002] In a three-phase four-wire control system, when the power equipment is off-grid with half-wave load, the midpoint balancing bridge circuit plays an indispensable role in balancing the positive and negative busbars. However, due to the limited maximum overcurrent capacity of the midpoint balancing current switch tube (such as the insulated gate bipolar transistor (IGBT)), the CBC point (Current Breaking Capacity Point, critical current breaking point) of the wave-by-wave current limiting is limited, which to some extent affects the maximum half-wave load capacity of the power equipment. Summary of the invention

[0003] The purpose of the present application is to provide a control method for an AC / DC converter, an electric power device and a computer-readable storage medium, aiming to solve the problem of limited load capacity of electric power equipment in a three-phase four-wire control system when it is off-grid and carrying a half-wave load in the related art.

[0004] In a first aspect, an embodiment of the present application provides a control method for an AC-DC converter, wherein the AC-DC converter includes an AC-DC converter and a balancing bridge circuit connected between a positive and negative DC bus of the AC-DC converter, and the control method includes:

[0005] Acquiring an AC side current of the AC-DC converter;

[0006] When the AC side current is a half-wave current, the balancing bridge circuit is controlled to operate continuously in each AC cycle to perform energy transmission.

[0007] In one embodiment, controlling the balanced bridge circuit to continuously operate and perform energy transmission in each AC cycle includes:

[0008] When the current amplitude of the AC side current is higher than a preset threshold, outputting a first drive signal, wherein the first drive signal is used to drive the balancing bridge circuit to generate a first current;

[0009] When the current amplitude of the AC side current is lower than a preset threshold, outputting a second drive signal, wherein the second drive signal is used to drive the balancing bridge circuit to generate a second current;

[0010] Wherein, the first current and the second current are both greater than zero.

[0011] In one embodiment, when the current amplitude of the AC-side current is lower than a preset threshold, outputting a second driving signal includes:

[0012] Obtaining the positive DC bus voltage, the negative DC bus voltage, and the midpoint balance current of the balance bridge circuit;

[0013] Obtaining the difference between the positive and negative DC bus voltages based on the positive DC bus voltage and the negative DC bus voltage;

[0014] When the current amplitude of the AC-side current is lower than the threshold, setting the given value of the positive and negative bus difference to a first given value, where the first given value is a non-zero value;

[0015] Obtaining the second driving signal based on the first given value, the difference between the positive and negative DC bus voltages, and the midpoint balance current.

[0016] In one embodiment, obtaining the second driving signal based on the first given value, the difference between the positive and negative DC bus voltages, and the midpoint balance current includes:

[0017] Calculating a given value of the first midpoint balance current based on the difference between the first given value and the difference between the positive and negative DC bus voltages;

[0018] Calculating the first target duty cycle based on the difference between the first midpoint balance current and the given value of the midpoint balance current;

[0019] Obtaining the second driving signal based on the first target duty cycle.

[0020] In one embodiment, the AC-DC converter further includes a first balancing capacitor and a second balancing capacitor connected between the positive and negative DC buses, and the capacitance values of the first balancing capacitor and the second balancing capacitor are equal; setting the given value of the positive and negative bus difference to the first given value includes:

[0021] Obtaining the total energy value transmitted by the balance bridge circuit in the previous AC cycle;

[0022] Updating the required energy value that the balance bridge circuit needs to transmit in the current AC cycle when the current amplitude of the AC-side current is lower than the threshold based on the total energy value;

[0023] Determining the first given value based on the required energy value, the capacitance value of the first balancing capacitor, the positive DC bus voltage, and the negative DC bus voltage.

[0024] In one embodiment, the sum of the positive DC bus voltage and the first given value is less than or equal to the positive DC bus overvoltage value; the difference between the negative DC bus voltage and the first given value is less than or equal to the negative DC bus undervoltage value.

[0025] In one embodiment, when the current amplitude of the AC-side current is higher than a threshold, outputting a first driving signal includes:

[0026] Obtaining the positive DC bus voltage, the negative DC bus voltage, and the midpoint balance current of the balance bridge circuit;

[0027] Obtaining the positive and negative DC bus voltage difference according to the positive DC bus voltage and the negative DC bus voltage;

[0028] When the current amplitude of the AC-side current is higher than the threshold, setting the positive and negative bus difference given value to a second given value, where the second given value is zero;

[0029] Obtaining the first driving signal according to the second given value, the positive and negative DC bus voltage difference, and the midpoint balance current.

[0030] In one embodiment, obtaining the first driving signal according to the second given value, the positive and negative DC bus voltage difference, and the midpoint balance current includes:

[0031] Calculating the given value of the second midpoint balance current according to the difference between the second given value and the positive and negative DC bus voltage difference;

[0032] Calculating the second target duty cycle according to the difference between the second midpoint balance current and the given value of the midpoint balance current;

[0033] Obtaining the first driving signal according to the second target duty cycle.

[0034] In a second aspect, an embodiment of the present application further provides a power device, including an AC-DC converter, a memory, a processor, and a computer program stored in the memory and executable on the processor. The AC-DC converter includes an AC-DC converter and a balance bridge circuit connected between the positive and negative DC buses of the AC-DC converter. The AC side of the AC-DC converter is used to connect to the power grid and / or load. The AC-DC converter is connected to the processor. When the processor executes the computer program, the steps of the control method of the AC-DC converter as described above are implemented.

[0035] In a third aspect, an embodiment of the present application further provides a computer-readable storage medium storing a computer program, which when executed by a controller can implement the steps of the control method of the AC-DC converter as described above.

[0036] The beneficial effects of the embodiment of the present application compared with the related art are as follows: In the control method of the AC-DC converter provided by the embodiment of the present application, when it is detected that the AC-side current is a half-wave current, for example, in the case of a half-wave load, the balance bridge circuit is controlled to continuously operate for energy transfer within each AC cycle, avoiding concentrating the process of energy transfer of the balance bridge circuit in the half AC cycle where the half-wave current is located, thereby causing overcurrent of the midpoint balance current and triggering wave-by-wave current limiting, which affects the maximum half-wave load-carrying capacity of the system. In this way, without the need to increase the maximum overcurrent capacity of the switching tubes, the half-wave load-carrying capacity is improved through software control. Therefore, the control method of the AC-DC converter provided by the embodiment of the present application improves the half-wave load-carrying capacity of the AC-DC converter. Description of the Drawings

[0037] Figure 1 is a schematic structural diagram of the AC-DC converter provided by the embodiment of the present application;

[0038] Figure 2 is the current waveform of the AC-DC converter provided by the embodiment of the present application;

[0039] Figure 3 is a flowchart of the control method of the AC-DC converter provided by an embodiment of the present application;

[0040] Figure 4 is a flowchart of the control method of the AC-DC converter provided by an embodiment of the present application;

[0041] Figure 5 is a control loop diagram of the control method of the AC-DC converter provided by an embodiment of the present application;

[0042] Figure 6 is a control loop diagram of the control method of the AC-DC converter provided by an embodiment of the present application;

[0043] Figure 7 is a schematic module diagram of the control device of the AC-DC converter provided by an embodiment of the present application;

[0044] Figure 8 is a schematic structural diagram of the power equipment provided by an embodiment of the present application. Detailed Embodiments

[0045] In order to make the technical problems, technical solutions and beneficial effects to be solved by this application clearer and more understandable, the following further details this application in combination with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not used to limit this application.

[0046] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of this application, "a plurality" means two or more, unless otherwise specifically defined.

[0047] As Figure 1 shown, a power device such as a power conversion system (PCS) is provided with an AC-DC converter. The AC-DC converter 100 includes an AC / DC conversion circuit 110 and a filter circuit 120. The first end of the filter circuit 120 is connected to the AC side of the AC / DC conversion circuit 110, and the second end of the filter circuit 120 serves as the AC side of the AC-DC converter 100. The DC side of the AC / DC conversion circuit 110 serves as the DC side of the AC-DC converter 100.

[0048] In the example, the main topology of the AC / DC conversion circuit 110 adopts a T-type three-level inverter circuit. The DC side of the T-type three-level inverter circuit is the positive and negative (DC) buses BUS+ / BUS-, and a first balancing capacitor C BUS1 and a second balancing capacitor C BUS2 are connected between the positive and negative DC buses BUS+ / BUS-. The midpoint of the bus is point O. Generally, the capacitance values of the first balancing capacitor C BUS1 and the second balancing capacitor C BUS are equal. The DC side of the T-type three-level inverter circuit is connected to the balancing bridge circuit 200; the AC side of the T-type three-level inverter circuit is connected to the filter circuit 120.

[0049] In the example, the filter circuit 120 can be an LCL filter circuit, and the LCL filter circuit is arranged on each phase output line of the T-type three-level inverter circuit. The filter circuit 120 includes filter capacitors C1, C2, C3 and filter inductors L 1a , L 1b , L 1c , L 2a , L 2b , L 2c . Taking phase A as an example, the LCL filter circuit of phase A includes inductor L 1a , capacitor C1 and inductor L 2a. After the output of the T-type three-level inverter circuit passes through the filter circuit 120, it is connected to the load through the off-grid and grid-connected circuit from the load interface and / or connected to the power grid through the power grid interface.

[0050] In the example, the balance bridge circuit 200 includes an upper switching tube M1 and a lower switching tube M2 connected in series between the positive and negative DC buses BUS+ / BUS-, and an inductor L3 with one end connected between the upper switching tube M1 and the lower switching tube M2, and the other end of the inductor L3 is connected to the midpoint O of the bus. The upper switching tube M1 and the lower switching tube M2 are, for example, IGBTs.

[0051] When the PCS operates off-grid with a half-wave load (such as small power appliances, lighting equipment, battery chargers), the situation of uneven voltage distribution between the positive and negative DC buses BUS+ / BUS- is likely to occur. In this regard, the balance bridge circuit 200 is used to control the voltage equalization between the positive and negative DC buses BUS+ / BUS- to achieve the potential balance of the midpoint O of the bus. However, the maximum overcurrent capacity of the switching tubes of the balance bridge circuit 200 is limited. If the power of the half-wave load is too large, the midpoint balance current i np0 (see Figure 2 ) is likely to trigger the CBC point (Current Breaking Capacity Point, critical current breaking point) of wave-by-wave current limiting. Therefore, the power of the half-wave load is limited by the maximum overcurrent capacity of the switching tubes, which to a certain extent affects the maximum half-wave load-carrying capacity of the power equipment.

[0052] In this regard, without changing the hardware, the embodiment of the present application provides a control method for an AC-DC converter that maximally utilizes the maximum overcurrent capacity of the switching tubes and improves the half-wave load-carrying capacity.

[0053] Please refer to Figure 1 、 2 and 3. The AC-DC converter control method provided by some embodiments of the present application includes:

[0054] Step S110, obtaining the AC-side current of the AC-DC converter.

[0055] Specifically, for example, a current sampling circuit is used to sample the currents of phases A, B, and C on the AC side of the AC-DC converter, that is, the currents passing through the filter inductors L 2a 、L 2b 、L 2c to obtain the AC-side current i 2a 、i 2b 、i 2c . It can be understood that when the AC-DC converter 100 operates off-grid with a load, the AC-side currents i 2a 、i 2b 、i 2c are also the load currents.

[0056] Step S120: When the AC-side current is a half-wave current, control the balance bridge circuit to continuously operate within each AC cycle for energy transfer.

[0057] Specifically, determine the waveforms of the AC-side currents i 2a , i 2b , i 2c . When the AC-side currents i 2a , i 2b , i 2c are half-wave currents, it indicates that the AC-DC converter 100 is operating with a half-wave load at this time. Here, the AC cycle (see t0 - t2 in Figure 2 ) refers to the cycle of the output current of the AC-DC converter 100, usually the local mains cycle, such as 1 / 50 s or 1 / 60 s. When the AC-side currents i 2a , i 2b , i 2c (see Figure 2 , only one phase i 2a is shown) are half-wave currents, it means that there is an output current only in the positive half-cycle (see t0 - t1, t2 - t4 in Figure 2 ) or the negative half-cycle (see t1 - t2 in Figure 2 ) of the AC cycle.

[0058] It can be understood that in the conventional case when the AC-DC converter 100 operates with a half-wave load, according to the requirements of the half-wave load, only half of the cycle of the AC-DC converter 100 needs to supply energy to provide the load current (i.e., the half-wave current), and the other half of the cycle is equivalent to no load. During the half-wave cycle with current, there must be unevenness between the positive and negative DC buses BUS+ / BUS-, that is, the positive and negative bus biases. At this time, it is necessary to extract energy from the positive DC bus BUS+ to the negative DC bus BUS- or from the negative DC bus BUS- to the positive DC bus BUS- through the balance bridge circuit 200 within this half-wave cycle. The larger the half-wave load, the greater the positive and negative bus biases. The midpoint balance current i np (i.e., the current flowing through the inductor L3) through the balance bridge circuit 200 within the half-wave cycle is also larger, which will ultimately trigger wave-by-wave current limiting and further affect the limiting of the load current. Obviously, using only half of the cycle to transfer energy (i.e., current) for bus balancing is easily restricted by the maximum overcurrent capacity of the switching tubes of the balance bridge circuit 200, which greatly affects the maximum half-wave load capacity. And during the other half of the cycle, the balance bridge circuit 200 is completely idle and no energy transfer is required.

[0059] See Figure 2 , for the three-phase AC-side current i 2a (only one phase is shown) with the same half-wave load and the midpoint balance current i nnp when the method of the present application is not adopted.and the midpoint balance current i after adopting the method of the present application nnp0 The current schematic diagram. From Figure 2 It can be seen that in the embodiment of the present application, within each AC cycle, the control balance bridge circuit 200 is continuously operated for energy transfer, and the formed midpoint balance current i nnp has a peak value much smaller than the midpoint balance current i nnp0 formed when only half a cycle is used for energy transfer. Obviously, in the case of the same half-wave load, this can avoid concentrating the process of the balance bridge circuit 200 for energy transfer within half an AC cycle, causing the midpoint balance current i nnp0 (such as at time t3) to overcurrent and trigger wave-by-wave current limiting. It can be understood that by controlling the balance bridge circuit 200 to continuously operate for energy transfer within each AC cycle, the total energy transferred by the balance bridge circuit 200 in each AC cycle can be increased. Therefore, a larger positive and negative bus bias can be allowed within the half-wave period of the half-wave load, thereby improving the maximum half-wave load capacity without replacing the switching tubes.

[0060] It can be understood that according to different types of loads, the currents of phase A, phase B, and phase C on the AC side of the AC-DC converter may have current in only one phase or multiple phases, and the present application does not limit this.

[0061] In some embodiments, the control balance bridge circuit continuously operates for energy transfer within each AC cycle in step S120, including:

[0062] Step A, when the current amplitude of the AC side current is higher than a preset threshold, output a first drive signal, and the first drive signal is used to drive the balance bridge circuit to generate a first current, where the first current is greater than zero.

[0063] It can be understood that according to the power supply requirements of the half-wave load and considering system errors such as sampling errors and filtering errors, the preset threshold can be a relatively small value close to 0. The current amplitudes of the AC side currents i 2a 、i 2b 、i 2c being higher than the preset threshold indicates that the half-wave load is in a state of having energy (i.e., power) demand at this time. Assuming that the positive and negative bus biases caused by the half-wave load within the half-wave period require the energy transferred between the positive and negative buses by the balance bridge circuit 200 in each AC cycle to be the equalization energy demand of the balance bridge circuit 200, then the first current i np1 driven by this step to generate the balance bridge circuit 200 is a part to meet this equalization energy demand. It can be understood that the remaining part of the equalization energy demand is provided by the second current i np2 generated by step B, see Figure 2 .

[0064] Step B, when the current amplitude of the AC - side current is lower than a preset threshold, output a second driving signal, where the second driving signal is used to drive the balanced - bridge circuit to generate a second current, and the second current is greater than zero.

[0065] It can be understood that when the current amplitudes of the AC - side currents \(i\) 2a , \(i\) 2b , \(i\) 2c are lower than the preset threshold, it means that the half - wave load is in a state of no energy demand at this time. However, the balanced - bridge circuit 200 still operates for energy transfer to supplement the other part of the balanced energy demand in this AC cycle or an adjacent AC cycle of the half - wave load. The second current \(i\) np2 generated by driving the balanced - bridge circuit 200 in this step is to meet the other part of the balanced energy demand.

[0066] Among them, the first driving signal and the second driving signal are, for example, pulse - width modulation (PWM) signals with a duty cycle greater than 0, which drive the upper switch M1 and the lower switch M2 of the balanced - bridge circuit 200 to cooperate with the inductor L3 to store and release energy, so as to output the first current \(i\) np1 and the second current \(i\) np2 .

[0067] Please refer to Figure 4 , in some embodiments, when the current amplitude of the AC - side current is lower than the preset threshold in step B, outputting the second driving signal includes:

[0068] Step S121, obtain the positive DC - bus voltage, the negative DC - bus voltage, and the mid - point balance current of the balanced - bridge circuit.

[0069] Specifically, for example, use a voltage - sampling circuit to sample the positive DC - bus voltage and the negative DC - bus voltage respectively. Use a current - sampling circuit to sample the current flowing through the inductor L3 of the balanced - bridge circuit 200 as the mid - point balance current \(i\) np .

[0070] Step S122, obtain the difference between the positive and negative DC - bus voltages according to the positive DC - bus voltage and the negative DC - bus voltage.

[0071] That is, take the difference between the positive DC - bus voltage \(V_{bus}\) + and the negative DC - bus voltage \(V_{bus}\) - to obtain the difference \(\Delta v\) pn between the positive and negative DC - bus voltages.

[0072] Step S123, when the current amplitude of the AC - side current is lower than the threshold, set the given value of the positive - negative bus difference to a first given value, where the first given value is a non - zero value.

[0073] The given value of the difference between the positive and negative busbars can be determined according to the difference between the balanced energy demand of the half-wave load in each AC cycle and the energy already transmitted in the half-wave cycle in step A. The first given value ΔV ref is set to a non-zero value. One reason is to be able to generate the second current i nnp2 to allow power transfer between the positive and negative DC buses BUS+ / BUS-. The other reason is that at this time, the half-wave load has no energy demand, which is equivalent to being unloaded. Therefore, a certain positive and negative busbar bias does not affect the load. See Figure 2 . The first given value ΔV ref is set to compensate for another part of the energy demand of the half-wave load in this AC cycle or an adjacent AC cycle in step B.

[0074] Specifically, assuming that the half-wave load has current in the positive half-cycle and no current in the negative half-cycle in each AC cycle, then energy needs to be transferred from the negative DC bus BUS- to the positive DC bus BUS+. Conversely, if there is current in the negative half-cycle and no current in the positive half-cycle, then energy needs to be transferred from the positive DC bus BUS+ to the negative DC bus BUS-.

[0075] Step S124, obtain the second driving signal according to the first given value, the voltage difference between the positive and negative DC buses, and the midpoint balance current.

[0076] Specifically, input the first given value ΔV ref and the voltage difference Δv between the positive and negative DC buses pn into the voltage control loop of the balance bridge circuit 200 to obtain the current reference value, and input the current reference value and the midpoint balance current i np into the current control loop of the balance bridge circuit 200 to obtain the second driving signal.

[0077] Please refer to Figure 5 , in some embodiments, step S124 includes:

[0078] Step S1241, calculate the given value of the first midpoint balance current according to the difference between the first given value and the voltage difference between the positive and negative DC buses.

[0079] The first PI controller of the voltage control loop of the balance bridge circuit 200 performs deviation calculation on the first given value ΔV ref and the voltage difference Δv between the positive and negative DC buses pn to obtain the given value of the first midpoint balance current.

[0080] Step S1242, calculate the first target duty cycle according to the difference between the first midpoint balance current and the given value of the midpoint balance current.

[0081] The first PI controller of the current control loop of the balance bridge circuit 200 performs deviation calculation on the first midpoint balance current i npPerform a deviation operation with the given value of the midpoint balanced current to obtain the first target duty cycle.

[0082] Step S1243, obtain a second drive signal according to the first target duty cycle.

[0083] The PWM modulator outputs a second drive signal according to the first target duty cycle.

[0084] In some embodiments, setting the positive and negative bus difference given value to the first given value in step S123 includes:

[0085] Step S1231, obtain the total energy value transmitted by the balanced bridge circuit in the previous AC cycle.

[0086] As described above, for a half-wave load, there is current in the positive half cycle and no current in the negative half cycle in each AC cycle. Then, energy needs to be transferred from the negative DC bus BUS- to the positive DC bus BUS+; conversely, energy is transferred from the positive DC bus BUS+ to the negative DC bus BUS-.

[0087] Specifically, when the half-wave load has current in the positive half cycle, the total energy value Q transmitted by the balanced bridge circuit 200 in the previous AC cycle is Q = ∑Vbus_ * i np * D; when the half-wave load has current in the negative half cycle, Q = ∑Vbus + * i np * D. Where D is the duty cycle of the drive signal of the balanced bridge circuit 200. In some embodiments, it can also be calculated directly based on the average voltage of the positive and negative bus voltages, then Q = ∑Vbus average * i np * D.

[0088] Step S1232, update the required energy value that the balanced bridge circuit needs to transmit in the current AC cycle when the current amplitude of the AC-side current is lower than the threshold according to the total energy value.

[0089] Assume that the time when the current amplitude of the AC-side current is lower than the threshold is half an AC cycle. According to the balanced bridge circuit 200 or other requirements, another part of the energy Q1 that the balanced bridge circuit 200 is required to transfer within step B can be set as a percentage of the total energy Q, such as 50%.

[0090] Step S1233, determine the first given value according to the required energy value, the capacitance value of the first balancing capacitor, the positive DC bus voltage, and the negative DC bus voltage.

[0091] Specifically, the first given value ΔV can be obtained according to the following formula ref :

[0092] 1 / 2Q = 1 / 2 * C * (Vbus + + ΔV ref)^2 - 1 / 2 * C * (Vbus - -ΔV ref )^2

[0093] Where C is the capacitance value of the first balancing capacitor C BUS1 and the second balancing capacitor C BUS2 .

[0094] It can be understood that in the embodiments of the present application, the positive DC bus voltage Vbus + plus the first given value ΔV ref is less than or equal to the positive DC bus overvoltage value; the negative DC bus voltage Vbus - minus the first given value ΔV ref is less than or equal to the negative DC bus undervoltage value. This limitation can prevent the AC-DC converter 100 from shutting down due to overvoltage or undervoltage faults.

[0095] In some embodiments, when the current amplitude of the AC-side current is higher than the threshold in step A, outputting the first drive signal includes:

[0096] Step S125, obtaining the positive DC bus voltage, the negative DC bus voltage, and the midpoint balancing current of the balancing bridge circuit.

[0097] Specifically, for example, a voltage sampling circuit is used to sample the positive DC bus voltage and the negative DC bus voltage respectively. A current sampling circuit samples the current flowing through the inductor L3 of the balancing bridge circuit 200 as the midpoint balancing current i np .

[0098] Step S126, obtaining the difference between the positive and negative DC bus voltages based on the positive DC bus voltage and the negative DC bus voltage.

[0099] That is, the difference between the positive DC bus voltage Vbus + and the negative DC bus voltage Vbus - is calculated to obtain the difference Δv pn between the positive and negative DC bus voltages.

[0100] Step S127, when the current amplitude of the AC-side current is higher than the threshold, setting the given value of the positive and negative bus difference to a second given value, where the second given value is zero.

[0101] To control the voltage equalization of the positive and negative DC buses BUS+ / BUS- and achieve the potential balance of the bus midpoint O, the second given value ΔV ref0 is set to zero.

[0102] Step S128, obtaining the first drive signal based on the second given value, the difference between the positive and negative DC bus voltages, and the midpoint balancing current.

[0103] Specifically, the second given value ΔV ref0 , the difference Δv between the positive and negative DC bus voltages pn are input into the voltage control loop of the balance bridge circuit 200 to obtain a current reference value, and the current reference value and the midpoint balance current i np are input into the current control loop of the balance bridge circuit 200 to obtain a first drive signal.

[0104] It can be understood that when the current amplitude of the AC-side current is higher than the threshold value, it is half of the AC cycle with no energy demand in half-wave load. At this time, there is a large bias voltage between the positive and negative buses, and it is equivalent to being loaded. Therefore, the given value of the difference between the positive and negative buses is set to 0.

[0105] Please refer to Figure 6 , in some embodiments, step S128 includes:

[0106] Step S1281, calculating a given value of the second midpoint balance current according to the difference between the second given value and the difference between the positive and negative DC bus voltages.

[0107] The first PI controller of the voltage control loop of the balance bridge circuit 200 performs a deviation operation on the second given value ΔV ref0 , the difference Δv between the positive and negative DC bus voltages pn to obtain a given value of the first midpoint balance current.

[0108] Step S1282, calculating a second target duty cycle according to the difference between the second midpoint balance current and the given value of the midpoint balance current;

[0109] The PI controller of the current control loop of the balance bridge circuit 200 performs a deviation operation on the first midpoint balance current i np and the given value of the midpoint balance current to obtain a second target duty cycle.

[0110] Step S1283, obtaining a first drive signal according to the second target duty cycle.

[0111] The PWM modulator outputs a first drive signal according to the second target duty cycle.

[0112] Please refer to Figure 7 , this application embodiment also provides a control device for an AC-DC converter, including:

[0113] An acquisition module 701, configured to acquire the AC-side current of the AC-DC converter;

[0114] A control module 702, configured to control the balance bridge circuit to continuously operate for energy transfer in each AC cycle when the AC-side current is a half-wave current.

[0115] In one embodiment, the control module 702 includes:

[0116] A first driving unit, configured to output a first driving signal when the current amplitude of the alternating current side current is higher than a preset threshold, where the first driving signal is used to drive the balance bridge circuit to generate a first current;

[0117] A second driving unit, configured to output a second driving signal when the current amplitude of the alternating current side current is lower than the preset threshold, where the second driving signal is used to drive the balance bridge circuit to generate a second current;

[0118] Wherein, both the first current and the second current are greater than zero.

[0119] In one embodiment, the second driving unit includes:

[0120] A first acquisition subunit, configured to acquire the positive DC bus voltage, the negative DC bus voltage, and the midpoint balance current of the balance bridge circuit;

[0121] A first calculation subunit, configured to obtain the positive and negative DC bus voltage difference according to the positive DC bus voltage and the negative DC bus voltage;

[0122] A first setting subunit, configured to set the positive and negative bus difference given value to a first given value when the current amplitude of the alternating current side current is lower than the threshold, where the first given value is a non-zero value;

[0123] A first driving subunit, configured to obtain the second driving signal according to the first given value, the positive and negative DC bus voltage difference, and the midpoint balance current.

[0124] In one embodiment, the first driving subunit includes:

[0125] A first PI controller, configured to calculate a given value of the first midpoint balance current according to the difference between the first given value and the positive and negative DC bus voltage difference;

[0126] A second PI controller, configured to calculate the first target duty cycle according to the difference between the first midpoint balance current and the given value of the midpoint balance current;

[0127] A PWM modulator, configured to obtain the second driving signal according to the first target duty cycle.

[0128] In one embodiment, the first setting subunit is specifically configured to:

[0129] Acquire the total energy value transmitted by the balance bridge circuit in the previous AC cycle;

[0130] Update the required energy value to be transmitted by the balance bridge circuit during the current AC cycle according to the total energy value, when the current amplitude of the AC-side current is lower than the threshold value.

[0131] Determine the first given value according to the required energy value, the capacitance value of the first balance capacitor, the positive DC bus voltage, and the negative DC bus voltage.

[0132] In one embodiment, the sum of the positive DC bus voltage and the first given value is less than or equal to the positive DC bus overvoltage value; the difference between the negative DC bus voltage and the first given value is less than or equal to the negative DC bus undervoltage value.

[0133] In one embodiment, the first driving unit includes:

[0134] A second acquisition subunit, configured to acquire the positive DC bus voltage, the negative DC bus voltage, and the midpoint balance current of the balance bridge circuit;

[0135] A second calculation subunit, configured to obtain the difference between the positive and negative DC bus voltages based on the positive DC bus voltage and the negative DC bus voltage;

[0136] A second setting subunit, configured to set the given value of the positive and negative bus difference to a second given value when the current amplitude of the AC-side current is higher than the threshold value, where the second given value is zero;

[0137] A second driving subunit, configured to obtain the first driving signal based on the second given value, the difference between the positive and negative DC bus voltages, and the midpoint balance current.

[0138] In one embodiment:

[0139] The first PI controller is further configured to calculate the given value of the second midpoint balance current according to the difference between the second given value and the difference between the positive and negative DC bus voltages;

[0140] The second PI controller is further configured to calculate the second target duty cycle according to the difference between the second midpoint balance current and the given value of the midpoint balance current;

[0141] The PWM modulator is further configured to obtain the first driving signal according to the second target duty cycle

[0142] For the specific implementation manners and related beneficial effects of the control device of the AC-DC converter, please refer to the description of the specific embodiments of the above-mentioned control method of the AC-DC converter, which will not be elaborated here.

[0143] Please refer to Figure 1 、 2As shown in FIGS. 7 and 8, an embodiment of the present application further provides a power device 80, which includes an AC-DC converter 100, a memory 82, a processor 83, and a computer program 821 stored in the memory 82 and executable on the processor 83. The AC-DC converter 100 includes an AC-DC converter 110 and a balancing bridge circuit 200 connected between the positive and negative DC buses BUS+ / BUS- of the AC-DC converter 110. The AC side of the AC-DC converter 110 is used to connect to the power grid and / or load. The AC-DC converter 100 is also connected to the processor 83. When the processor 83 executes the computer program 821, the steps of the control method of the AC-DC converter as described above are implemented.

[0144] It can be understood that the power device 80 can be a single power device, or a battery pack with a battery module 801, or an energy storage device including multiple battery packs with battery modules 801.

[0145] Those skilled in the art can understand that Figure 8 merely examples of the power device 80, which do not constitute a limitation on the power device 80, may include more or fewer components than shown in the figures, or combine certain components, or different components, such as may also include input / output devices, network access devices, etc.

[0146] It can be understood that when the power device is a PCS, the AC-DC converter 100 can be a bidirectional AC-DC converter.

[0147] The processor 83 can be a central processing unit (CPU), and the processor 83 can also be other general-purpose controllers, digital signal controllers (DSPs), application-specific integrated circuits (ASICs), off-the-shelf programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose controller can be a microcontroller or any conventional controller.

[0148] The memory 82 may be an internal storage unit of the power device 80 or the energy storage device in some embodiments, such as the hard disk or memory of the power device 80 or the energy storage device. The memory 82 may also be an external storage device of the power device 80 or the energy storage device in other embodiments, such as a plug-in hard disk, a Smart Media Card (SMC), a Secure Digital (SD) card, a Flash Card, etc. equipped on the power device 80 or the energy storage device. Further, the memory 82 may also include both the internal storage unit of the power device 80 or the energy storage device and the external storage device. The memory 82 is used to store an operating system, application programs, a Boot Loader, data, and other programs, etc. The memory 82 may also be used to temporarily store the data that has been output or will be output.

[0149] An embodiment of the present application also provides a computer-readable storage medium storing a computer program 821, and when the computer program 821 is executed by a processor 83, the steps in the above method embodiments can be implemented.

[0150] An embodiment of the present application provides a computer program product, which when running on a computer, causes the computer to execute the steps in the above method embodiments.

[0151] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on such an understanding, to implement all or part of the processes in the above method embodiments of the present application, the computer program 821 can be used to instruct the relevant hardware to complete. The computer program 821 can be stored in a computer-readable storage medium. When the computer program 821 is executed by the processor 83, the steps in the above method embodiments can be implemented. Wherein, the computer program 821 includes computer program 821 code, and the computer program 821 code can be in the form of source code, object code, executable file, or some intermediate form, etc. The computer-readable medium may at least include: any entity or device capable of carrying the computer program 821 code to the photographing device / terminal device, a recording medium, a computer memory 82, a ROM (Read-Only Memory, read-only memory 82), a RAM (Random Access Memory, random access memory 82), a CD-ROM (Compact Disc Read-Only Memory, read-only optical disc), magnetic tape, floppy disk, and optical data storage device, etc. The computer-readable storage medium mentioned in the present application may be a non-volatile storage medium, in other words, it may be a non-transitory storage medium.

[0152] It should be understood that all or part of the steps for implementing the above embodiments can be realized by software, hardware, firmware, or any combination thereof. When implemented using software, it can be realized in whole or in part in the form of a computer program product 821. The computer program product 821 includes one or more computer instructions. These computer instructions can be stored in the above-mentioned computer-readable storage medium.

[0153] In the above embodiments, the descriptions of the respective embodiments have their own emphases. For parts not detailed or recorded in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0154] Those of ordinary skill in the art can realize that the units and algorithm steps of the examples described in combination with the embodiments disclosed herein can be implemented by electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are executed in hardware or software depends on the specific application and design constraints of the technical solution. Professional technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of this application.

[0155] In the embodiments provided in this application, it should be understood that the disclosed devices / electronic devices and methods can be implemented in other ways. For example, the device / electronic device embodiments described above are only illustrative. For example, the division of modules or units is only a logical function division. In actual implementation, there can be other division methods. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the displayed or discussed couplings or direct couplings or communication connections to each other can be through some interfaces. The indirect couplings or communication connections of devices or units can be in electrical, mechanical, or other forms.

[0156] The units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they can be located in one place, or distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0157] The above embodiments are only used to illustrate the technical solutions of this application, rather than to limit it; although this application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included in the protection scope of this application.

Claims

1. A control method for an AC / DC converter, characterized in that: The AC-DC converter includes an AC-DC converter and a balancing bridge circuit connected between the positive and negative DC bus bars of the AC-DC converter, and the control method includes: Acquiring an AC side current of the AC-DC converter; When the AC side current is a half-wave current, the balancing bridge circuit is controlled to operate continuously in each AC cycle to perform energy transmission.

2. The control method according to claim 1, characterized in that: The controlling the balanced bridge circuit to continuously operate and perform energy transmission in each AC cycle includes: When the current amplitude of the AC side current is higher than a preset threshold, outputting a first drive signal, wherein the first drive signal is used to drive the balancing bridge circuit to generate a first current; When the current amplitude of the AC side current is lower than a preset threshold, outputting a second drive signal, wherein the second drive signal is used to drive the balancing bridge circuit to generate a second current; Wherein, the first current and the second current are both greater than zero.

3. The control method according to claim 2, characterized in that: When the current amplitude of the AC side current is lower than a preset threshold, outputting a second driving signal comprises: Obtaining a positive DC bus voltage, a negative DC bus voltage, and a midpoint balancing current of the balancing bridge circuit; Obtaining a positive and negative DC bus voltage difference according to the positive DC bus voltage and the negative DC bus voltage; When the current amplitude of the AC side current is lower than the threshold, setting the positive and negative bus difference given value to a first given value, wherein the first given value is a non-zero value; The second drive signal is obtained according to the first given value, the positive and negative DC bus voltage difference, and the midpoint balance current.

4. The control method according to claim 3, characterized in that: The obtaining the second driving signal according to the first given value, the positive and negative DC bus voltage difference, and the midpoint balance current includes: Calculating a given value of a first midpoint balancing current according to a difference between the first given value and the positive and negative DC bus voltage difference; Calculating the first target duty cycle according to a difference between the first midpoint balancing current and a given value of the midpoint balancing current; The second driving signal is obtained according to the first target duty cycle.

5. The control method according to claim 3 or 4, characterized in that: The AC-DC converter further includes a first balancing capacitor and a second balancing capacitor connected between the positive and negative DC bus bars, and the capacitances of the first balancing capacitor and the second balancing capacitor are equal; and setting the positive and negative bus bar difference given value to a first given value includes: Obtaining a total energy value transmitted by the balanced bridge circuit in the last AC cycle; updating, according to the total energy value, a required energy value that the balancing bridge circuit needs to transmit in the current AC cycle when the current amplitude of the AC side current is lower than a threshold value; The first given value is determined according to the required energy value, the capacitance of the first balancing capacitor, the positive DC bus voltage, and the negative DC bus voltage.

6. The control method according to claim 5, characterized in that: The sum of the positive DC bus voltage and the first given value is less than or equal to the positive DC bus overvoltage value; the difference between the negative DC bus voltage and the first given value is less than or equal to the negative DC bus undervoltage value.

7. The control method according to claim 2, characterized in that: When the current amplitude of the AC side current is higher than a threshold, outputting a first drive signal comprises: Obtaining a positive DC bus voltage, a negative DC bus voltage, and a midpoint balancing current of the balancing bridge circuit; Obtaining a positive and negative DC bus voltage difference according to the positive DC bus voltage and the negative DC bus voltage; When the current amplitude of the AC side current is higher than the threshold, the positive and negative busbar difference given value is set to a second given value, wherein the second given value is zero; The first drive signal is obtained according to the second given value, the positive and negative DC bus voltage difference, and the midpoint balance current.

8. The control method according to claim 7, characterized in that: The obtaining the first driving signal according to the second given value, the positive and negative DC bus voltage difference, and the midpoint balance current includes: The given value of the second midpoint balancing current is calculated according to the difference between the second given value and the positive and negative DC bus voltage difference; Calculating the second target duty cycle according to a difference between the second midpoint balancing current and a given value of the midpoint balancing current; The first driving signal is obtained according to the second target duty cycle.

9. An electric power device, characterized in that: The invention comprises an AC-DC converter, a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the AC-DC converter comprises an AC-DC converter and a balancing bridge circuit connected between the positive and negative DC buses of the AC-DC converter, the AC side of the AC-DC converter is used to connect to a power grid and / or a load, the AC-DC converter is connected to the processor, and the processor implements the steps of the control method of the AC-DC converter according to any one of claims 1 to 8 when executing the computer program.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by the controller, the steps of the control method of the AC-DC converter according to any one of claims 1 to 8 can be implemented.

Images